A power converter such as a DC-DC converter is used for hybrid cars and electric vehicles. The power converter is provided with a cooler including a semiconductor module in which a semiconductor element such as a switching element is built and a heat exchange part to cool the semiconductor module. As the cooler used for the power converter, for example, a cooler shown in a patent document 1 can be given.
In the patent document 1 a power converter is disclosed which is provided with a cooler having a heat exchange part constituted of a plurality of cooling pipes. In the heat exchange part, a plurality of semiconductor modules and a plurality of cooling pipes are alternately stacked, so the heat exchange part is constituted in such a way that the semiconductor modules can exchange heat with a refrigerant flowing in refrigerant passages formed in the cooling pipes and hence can be cooled by the refrigerant.